This section provides background information related to the present disclosure which is not necessarily prior art.
In recent years it has become increasingly popular to provide vehicles with the ability to convert between two-wheel and four-wheel drive. As popularity has grown, so to have the many ways of affecting conversion. In one example there is a permanently driven drive line segment to the rear wheels of a vehicle, and a part-time driven drive line segment to the front wheels. The part-time driven drive line segment is simply disconnected/decoupled from the engine's drive shaft at the transmission or transfer case and that segment is rendered passive (undriven).
There is often a second point of disconnection which may be at or near the differential (a center disconnect) or at both wheels. There is a mechanical action that takes place to achieve each connection and disconnection as contemplated herein. Two shafts or drive line segments are in close relationship and a clutch ring that is permanently coupled to one shaft is slidable into engagement with the other shaft to couple the shafts and is slidable out of engagement with the other shaft to decouple the two shafts.
The sliding movement is achieved by what will here be referred to as an actuator. The actuator can be many types including, e.g., a shift lever, manual or electrically driven, it can be cam actuated and it can be pneumatically actuated.
Pneumatic actuators in general are not new. Pneumatic actuators of this kind are disclosed in commonly assigned U.S. Pat. Nos. 5,704,895; 6,109,411; and 6,234,289. In the above listed patents, the clutch ring and components to be coupled are rotating and the annular actuator is designed to shift a non-rotating member (referred to as a fork) that is placed in contact with the rotating clutch ring. The contact between the rotating clutch ring and fork is designed to form a bearing that permits rotation of the clutch ring while the entire actuator remains static. The annular configuration of the actuator which surrounds the juncture to be coupled enables the use of a greater surface area on which the air acts. Thus, the available air pressure (from the manifold) is being applied to the greater surface area and produces a greater accumulated force. The diaphragm that is used as the movable wall is made of material that conforms and seals against metal objects. Placing the diaphragm in an opening that needs otherwise to be sealed allows the diaphragm to serve dual purposes.
Having thus achieved a far more efficient air actuated clutch ring actuator, all or most of the actuators heretofore provided along the drive line are advantageously replaced with the annular actuator of the patented designs. Even with the improved performance and efficiency of the air actuated clutch ring actuator, additional improvements in the manufacture and assembly of the hub assembly have been developed. In particular, the present disclosure provides a compliant piston and shift fork assembly to reduce the risk of damage to the piston and shift fork assembly during assembly of the half shaft to the wheel end.